The AVW200 interface module applies a new method for measuring vibrating wire sensors using a very accurate frequency domain approach.
The traditional method uses a time-domain approach. The natural or resonant frequency at which the wire is oscillating is determined by exciting the wire with an AC excitation, stopping the excitation, and then measuring time between response pulses.
Eliminates the problem of incorrect readings due to noise sources.
Retrieves frequency of interest via SDI-12, RS-232, or PakBus network protocol
Supports standalone capability by using a wireless model (AVW206, AVW211, AVW216)
Provides low current drain (300 µA quiescent, 40 mA during 2-second measurement)
Includes dual channel coils plus a thermistor measurement
Simplified configuration and datalogger programming
In addition to refining the AC excitation, the new method featured in the AVW200 takes advantage of its built-in spectrum analyzer that uses spectral interpolation instead of the traditional pulse-timing approach. It samples the returned signal, performs an FFT (fast Fourier transform) to discriminate between spectral components, and then identifies and measures the resonant frequency of the sensor. This means that even in noisy environments the sensor's resonant frequency can be identified and accurately measured.
The new method also provides much better measurement resolution (improving from 0.01 Hz to 0.001 Hz) as well as diagnostic information about the measured frequency. This diagnostic information includes the signal-to-noise ratio, amplitude of the dominant frequency, and an optional spectrum showing all of the frequency components. The AVW200 can be used via SDI-12, RS-232, or PakBus network protocol. Its low power consumption and rugged design match the durability and long-term stability of vibrating-wire sensors.
The AVW211 has the same features and capabilities as the AVW200, with the addition of an internal spread-spectrum readio for wireless communication. The radio operates in the 920- to 928-MHz frequency range, suitable for New Zealand.